Bibcode
DOI
Noël, Noelia E. D.; Gallart, Carme; Costa, Edgardo; Méndez, René A.
Bibliographical reference
The Astronomical Journal, Volume 133, Issue 5, pp. 2037-2052.
Advertised on:
5
2007
Citations
49
Refereed citations
38
Description
We present ground-based B- and R-band color-magnitude diagrams (CMDs)
reaching the oldest main-sequence (MS) turnoffs with good photometric
accuracy for 12 fields in the Small Magellanic Cloud (SMC). Our fields,
located between ~1° and ~4° from the center of the galaxy, are
situated in different parts of the SMC such as the ``Wing'' area and
toward the west and south. In this paper we perform a first analysis of
the stellar content in our SMC fields through comparison with
theoretical isochrones and color functions (CFs). We find that the
underlying spheroidally distributed population is composed of both
intermediate-age and old stars and that its age composition does not
show strong galactocentric gradients. The three fields situated toward
the east, in the Wing region, show very active current star formation.
However, only in the eastern field closest to the center do we find an
enhancement of recent star formation with respect to a constant SFR(t).
The fields corresponding to the western side of the SMC present a much
less populated young MS, and the CF analysis indicates that the SFR(t)
greatly diminished around 2 Gyr ago in these parts. Field smc0057, the
closest to the center of the galaxy and located in the southern part,
shows recent star formation, while the rest of the southern fields
present few bright MS stars. The structure of the red clump in all the
CMDs is consistent with the large amount of intermediate-age stars
inferred from the CMDs and color functions. None of the SMC fields
presented here are dominated by old stellar populations, a fact that is
in agreement with the lack of a conspicuous horizontal branch in all
these SMC CMDs. This could indicate that a disk population is ruling
over a possible old halo in all the observed fields.